Telephone automatic trunking system.



E. U. FALES.

TELEPHONE AUTOMATIC TRUNKING SYSTEM.

Patenwd Feb`A 26, 1918.

S SHEETS--SHEET I.

E. D. FALES.

TELEPHONE AUTUMATIC TRUNKING SYSTEM.

APPLICATION FILED AUG.IO. 190?.

1 ,257,832. Patented Feb. 26, 1918.

0% 7a 35554633 A Kiwa/6272503.-

E. D. FALES.

TELEPHONE AuToMATIc TRUNKING SYSTEM.

APPLICATION FILED AUGJO. |901.

Patented Feb. 26, 1918.

8 SHEETS-SHEET 3.

E. D. FALESV TELEPHONE AUTOMATIC TRUNKING SYSTEM.

APPLICATION FILED AUG. l0. |901.

Patented Feb. 26,1918.

8 SHEETSwSHEET 4.

E. D. mss TELEPHONE AUT'JMATIC TRUNKING SYSTEM.

l APPLICATION FILED AUG.10.\901.

Patented Feb. 26,1918.-

s sums-sain 6.`

E. n. mis. TELEPHON AUTOMATIC TRUNKING SYSTEM.

`AIPLHMTION FILED AUG. 10, |907.

1,257,832. Patented Feb. 26,1918.

8 SHEETS-SHEET E. D. FALES'.

TELEPHONE AuroMATlc RuNKmG svsrEM.

APPLICATLON FILED AUG. l0. i901.

` Patented Feb. 26', 1918.

8 SHEETS-SHEET 8.

UNITED sTATEs PATENT oEE'IoE.

' 'EDWARD D. EALEs, or LA GRANGE, ILLINOIS, AssIeNoE, EY MEsNE' ASSIGNMENTS, To

AUTOMATIC ELECTRIC COMPANY, A o'oEPoEATIoN 0E ILLINoIs.

- TELEPHCNE AUTOMATIC TRUNKING SYSTEM.

To all 'whom 1f/may concern.'

Be itknown that I, EDWARD D. FAITES, a citizen of the United States of America, and resident of La Grange, Cook county, Illinois,

have invented a certain new and useful Improvementjin Telephone Automatic Trunk- 1ng Systems, of" which the following is a 'connection with `the called telephone lines'.`

In systemsof this kind it isold to provide the subscribers lines with individual trunking switches -for automatically selecting trunks leading. tofirstfselectors. It has also.

ffbeen proposed to employ more thanone preliminary trunkin'g or `non-numerical swltch between the calling subscribers line andthe -rst-seleetorfthat is to say, to employ subT scribers individual switches for selecting iitrunks leading to non-numerical switches,

the latter being'r adapted to then select idle trunks leading to the first-selectors. The socalled first-selectors are' the automatic switches that perform trunking operations corresponding to the first digiti 0f ally Called number, and are well known and understood. In accordance with my invention, however, and-"as herein disclosed, pr1mary and secondary prelimlnary-tru'nking or nonvnumerical switches are employedbetween'the ilcal trunking switches, which are' individualv subscriberslines and the 'first-selectors, but the said secondary non-numerical trunking switches do lnot select Atrunks leading to the first-selectors. The said primary nonnumerito the subscribers lines, select'idletrunks, and the said secondary nonfnumericalftrunk ing switches select the same trunks-fthat is to`; say, whenever. a subscribers individual switch seizes; a trunk, a preselected secondary non-numerical trunking switch then promptlyY seizesv the other end ofthe same trunk. n vthis way the-intermediate trunks which extend from the primary-non-numeri'4` f cal switches to the secondary non-numerical switches are provided at' each end with multiple bank-contacts, and the automatictrunking switches thus arranged at each 'end of Specification of Letters Patent. i Patented Feb. 26, 1918. Appueaaon mea Augut 1o, 1901. serial No. 357,948.

said intermediate trunks are all common to` to the banks of the secondary non-numerical trunking switches. Another common mechf anisml controls the voperations of the said secondary non-numerical trunki'n switches,

whereby the calling subscriber a so obtains connection* with a, preselected trunk runni to a Erst-selector. This arrangement, I iin tends to distribute the work among th' diff ferent trunk lines, and more evenly between the different first-selectors, so that no one trunkline 'or no one first-selector, will be the others. The nature and 'advantages of my invention', 'however',"w1ill hereinafter more fully appear. l l

In the accompanying drawings Eigure'l's Vsuloject'to more use and wear and tfearthan a. diagram illustrating the arrangement of f the switches usedbyfa subscriber" M, whose line terminates in a district or "sub-central station, in a-'sytem embodying the principles of my invention. At"- A 4 is' indicated a group of trunk lines; at B a group of trunking `switches to'which said trunk lines are common; and at C asecond group of trunkng auxiliary switches` whichl are adaptedfto shift from trunk line to trunk lineg- In this iigure there is indicated a s'o-'called plunger shaft D .which iscommon to the group o f switches B. At E1 there is also shown a socalled master switch for controlling the plunger sha'tYD'. At F- there is shown another plungershaft which is'common to 'the group of switches C, and at Gr a master switch (similar to the master switch El) for "controlling the shaft F, and, therefore, for controlling the position of the idle switches C with regardto the trunk-lines A. At H thereisA a'mas'ter switch" the function of'l which is to pick out the switch C to be operated and at lI there is indicated a group o.

Fi Qshows .the -arrangement of the switc es used by a subscriber L, the line of whose telephone terminates directly in the 10s first selectors, one allotted to each of the A switches C .together, illustrate the apparatus brought (in a ten-thousand system embody- Fig. 4 is a diagram of one of the line switches J of the 'group of switches B, and of the aster switch E shown at the right. It willxbe seen that the circuit connections of these two switches, and the circuit connection between them, are shown. The master switch E comprises a bank K of circuit terminals in connection with which a suitable wiper operates.

Fig. 5 is a front or edge viewof the said bank K.

Figs. 6, 7 and S are diag-ams which, taken into use ing my invention) to establish and maintain a connection between the callingsubscriber L and the called subscriber M. This apparatus (following the arrangement indicated in Fig. 2) consists (Fig. 6) of a calling subscribers station L, a callingsubscribers trunking individual or lineI switch J, a controlling master switch E, an auxiliary switch N and an auxiliary master circuit-switch Il; Fig. 7, a so-called firstselector O and a second-selector P; Fig. 8, a so-called connectoigR', the called subscribers" individual line switch S and the called subscribers station M. p

Fig. 9 is a perspective4 of the so-called impulse springs alloted to each subscribers station, through the medium of which impulses are transmitted to the central station or stations for the purpose of operating the automatic switching devices.

Figs. 10, ,11, 12, 13,14 and 15 illustrate the positions of the said impulse springs at different stages of an operation.

Fig. 16 is a diagram showing the arrangement of the switching apparatus used by the district substation M in calling. This comprises thetwo master vI have elected to illustrate.

switches E? and G, as indicated in Fig. 1.

The substatons in connection with `which .iy invention may be of any suitable or approved type.' VThe substation L (Fig. 6), for example, is equipped with the ordinary receiver 2, switchhook 3, transmitter 4, battery 5, inductioncoil 6 and ringer 7. Being an automatic substation it is, in addition, provided with certain more or details, and with suitable circuits. It-` will be seen that the switch-hook 3 is provided with a set of cam arms 8, 9 and 10. The

n, arm 8 is used for controlling the ground Y isA circuit yat a pointbetween the so-called ground springs l1 and 12, and is also used `to the rear end of which is `25 to clear the angled terminal vnamely the lu less well-known mechanical vertical impulse teeth for controllin the' cam. latch through the medium of w ich the dial (which is not shown) is maintained normally locked, sol

coming into contact until after thedial has been'operated. The arm 9 acts as a contact arm which, when the receiver is on the switch-hook, engages vthe so-called` circuit spring 14', whereby the ringer 7, in series with the condenser 15, is bridged across the line conductors 16 and 17. The arm 10 has under its control the so-called release springs 18, 19 and 20 through the medium of which the line conductors 16 and 17 are grounded simultaneously for the purpose of releasing the switching-apparatus. Through the center of the apparatus there passes a shaft 21 l rigidly secured the dog 22. The so-called impulse wheel 23 is secured near the middle of said shaft, and the dial, already mentioned, at the front end thereof. The dog 22 has a pin 211 on its end in front of which the latch 13 normally rests for the purpose of locking the dial, as already explained. It'should be stated, how ever, that when the receiver is removed from the switch-hook the arm 8 barely raises the latch 13enough to permit the dial to rotate,v

but vnot enough to vcause the insulating tip l of the ground spring 12. -When the dial is rotated, however the latch 13 is raised still a little higher by the pin 24- which passes under the rounded end of the latch 13, by which operation the insulating -tip 25 is driven oli of the spring 12, permitting the latter to engage the spring 11 and thus close the` subscribers ground circuit.. This substation is equipped with the usual vertical and rotary impulse springs 26 and 27 (see Fig. 9) which are of a special construction. These springs 26 and 2T are provided on their under side with lugs 28v and 29, respectively.

28is adapted to be engaged by the so-cal ed vertical impulse teeth -30 on the periphery of the impulse wheel 23, p while the lu 29 is adapted to be engaged by the so-cal ed rotary impulse tooth 31ton the same wheel. It will be seen that the rotary impulse spring 27 isY provided with an auxiliary lug 32 which, when the dial is turneddown, is engaged by the rotary impulse tooth 31, and as a result the rotary impulse spring 27 is long contact with spring 33 (Fig. 11).

the so-called Gfround At this operatlon the 30 pass the lug V2S without carryingthe vertical impulse spring 26 onto the ground spring 33 (Fig. 13) but as the dial returns each impulse tooth will press the vertical impulse spring 26 once onto the ground post 33. After the last vertical nnpulse-has been delivered, then the The formengiven a comparativelyimpulse tooth 31again presses thc rotary A ,impulse spring 27 onto the ground post 33,

but this Ytime 1t does so by directly engagmitting ap aratus in normal condition. Fig. 11 shows t e apparatus at the stage where the rotary impulse tooth 31 has engaged the auxiliary member 32, and it, will be seen that the rotaryv impulse spring 27 is thereby .j pressedI onto t e ground post 33. Fig. 12

Yshows. the rotary tooth 31 ,ashaving just cleared. the member 32, and the rotary impulse spring 27 as having been released. .One of the vertical impulse teeth is shown as havingadhvanced beyond the lug 28 of the I vertical impulse spring 26. Fig. 13 shows vthe dial still farther advanced. Fig. 14 'showsfone of the vertical teeth engaging the rotary impulse spring 26, pressing the latter 'onto the ground post 33. Fig. 15 shows the Arotary impulse tooth 31 as having engaged the rotary impulse spring 27 dircctl on the return stroke, and as having passe behind the auxiliary member 32 and thus again pressed the impulse .s ring 27 onto the ground post 33. By re erring to station L (Fig. 6) it will be seen that when the switch hook is down the arm 9, upon engaging the spring 14, causes the'latter to separate the secondary circuit springs 36 and 37.

.primary circuitsprings 34 and 35 and the This is illustrated at substation M (Figf8). |The substation L is :further provided with a sig-l naling button 38v that controls the spring 39, which latter normally rests 4in engagement with the contact 40 but which, when z a spring terminal bank Q and an operating l'l'" plunger 42, together with meansv for operating said plunger 42, which means consists in af plunger shaft '43 controlled exclusively by the ,masterswitch E", a trip magnet 44 and release ma 'et 45. In ordertoshow- "y" clearly'the relation between the bank termivnalQand the plunger 42A of the line switch,

the bank Q is shown turned around from its true position with respect to the swing ofthe 4plunger 42, and, of, course, the insulating """termina'l 46 o n the end of said plungerl is correspondingly turned. The plunger 42 is loosely'pivoted on the end of the plunger arm 47., and is normally held in enga ement lthe shaft V43 in opposition to t 'e 'terision.. of the spring 48.'l The release lmagnet 45, it will-'be seen, is provided with an armature l49 which, on lts forward end,4 carries. .pivotally secinedl thereto a second-'a1'-A mature. 50 controlled by the trip magnet 44. f

Normallyv the forwardV end 51 of the trip f armature 50 is adapted to engage the rear terminal 52 of the plunger arm 47, for the purpose of retaining the plunger 42 in engagement with the plunger shaft 43. The tension of the spring 48, it lwill be seen, is overcome by the tension of the spring 53,

'which latter is adapted to retain the re.-

lease armature 49 normally against the stop 54. Ofcourse, when the trip magnet 4.4 atltracts its armature 50 the terminal 51 is 'disengaged from the rear terminal 52 of the plunger arm 47, thus leaving the plunplurality of jack-like sections, one of which is shown at g comprising the springs 55, 56,

57, 58 59, 60v Gland 62. In this bank, it should jacks q are in multiple, likewise all springs 56, all springs 59, and all springs 60; while the springs 57, 58, 6l and 62 are not connected, but are'all individual springs. The line switch J has, in addition, the so-called cut-off relay 63 which controls the springs 64, 65 and 66. It is obvious, of course, that the various parts (except the bank Q and shaft 43) may be mounted upon any suitable frame or base. The usual dimensions of this base arefive inches long, four inches wide and one inch deep, the plunger-arm 47 extending out about' two inches beyond the length. It is customary to mount the ger to the action of thespring 48. The bank Q, it will be understood, is made up o'l' aA be explained, all the 'springs55 of the sections g in a row in front of the switches on a separate support.

The master switch l E is a simple device comprising a motor magnet 67, a motor' magnet relay 68, the bank K, the ratchet wheel 69, a wiper 70 and a cam arm 71. Said motor ma gnetfis equipped with an interrupter which may be of any suitable character. for example of the type described in United States Patent No. 841,004, granted January 8, 1907, to John Erickson. This interrupter, as shown, comprises the springs 72 and 73 directly included in the circuit, and an auxiliary or latch spring 74. The motor magnet is also provided With an armature 75 on the end of which there is pro. vided. a pawl 76, the limit` of stroke of which is markedby the stop 77. lThispawl 76 is provided for 'the purpose of operating; is

the ratchet wheel 69,v which latter equipped on one of its sides withfa set of pins'78, 79, 80 and 81. It will be seen thatthe cam arm -71 is resting in engagement with" the pin 7 8; but by causing the ratchet wheel 69 to advancel a number of steps thepin 78 will be carried beyond the reach of; the cam 79; and then by another series of steps, pref- Aerably ten in number, the pin,79 will in ico 71, which latter will then fall ontoY the pin I 71, andthe said cam will thenfall against the'pin 80, and so on. WVhen the cam arm 71 first falls upon the pin 79 thel wiper 70 is adjusted to engage the first set of contacts of the bank K, namely the contacts 82 and 83, and each time that the magnet 67 is energized thereaftei` the wiper 70 is advanced one step intoengagement with another contact. In this way, it will be seen, nine suc- 5 cessive steps of the wiper 70, after said wiper leaves the first set of contacts 82 and 83, will bring the wiper 70 onto the last set of contacts 84 and 85. It will be obvious that at the next step thereafter the cam arm 71 will leave the pin 79 and meet the contact point 80, at which operation the wiper 70 will pass back into engagement with the iirst set of contacts-82 and 83. It will be seen that the ratchet wheel 69 is provided with a pawl to insure the wheel against backward rotation. As shown, the motor magnet relay 68 is provided with two windings 86 and 87, the use of whichl will be explained. This relay 68, as shown, controls the springs 88 and 89 comprised in the energizing circuit of the motor magnet 67. The bank and wiper of the master switch E is shown diagrammatically in Fig. 4, but Fig, 5 shows one of the forms of construction of thc bank as it appearsY in actual practice. The wiper 70 is shown made up of a front part a and a rear part b, the part b -playing over theicontacts a: and the common segment ai', while the part a plays over the contacts y and the common segment y. In Fig. i t" section a is a; wiper separate and distinct from the wiper b. These wipers a. and b may be of the type described in connection with the connector switch shown in United States Patent No. 815,176, granted March 13, 1906, to Keith, `Erickson & Erickson, and known as the private wiper, which consists of a spring finger with a bifurcated terminal, which terminal, as indieated, is the one that slides over the contacts on one side and the common segment on the other. It will be seen, furthermore, that on the return motion of wthew'ipers to first position they do-not pass over the contacts, but instead ride over the insulated 4springs 90 and 91, from which springs they drop upon reaching a position' opposite the first set of contacts 82- and 83. It will be understood, of course, that the ,same 'motion that has been described for the, wiper 70 is transmitted to the plunger shaft v43. which motion, as already explained, oscillatory incharacter; but it should be borne in mind that at no time does the channel 93 of this.

shaft pass to aposition Where any plunger 42 may not assume its normal position in engagement therewith.' In Fig. 4 there is-shown a relay 92' which neither belongs to the line switch J not to the master switch E, but which is provided for every bank jack g-thatvis, one is providedfor every trunk line leading from, the bank terminal g. The object and function of this relay will become apparent. The auxiiary line switch N (Fig. G) is substantially the same mechanically as the line switch J. The circuits, however, are modified to accomplish .certain purposes, as will be seen. As shown said switch N isprovided with the usual plunger 94, trip magnet 95 and release magnet 96. The plungers of these auxiliary switches N, with the arrangement shown in Fig. 6 are controlled by the same plunger shaft 43 that controls the switches J. This, however, is not always essential, as will be explained in connection with Fig. 6.

By referring to Fig. 2 it will be seen that the section of the shaft allotted to the auxiliary switches C is of diferent construction from the section of the shaft allotted tothe. switches B. The 'group of switches B are permitted to bring their plungers directly in contact with the shaft, but the plungers of the switches C are not permitted to thus come into contact with the main shaft. Each plunger of the auxiliary switches C has allotted to it an insulated metallic strip c (Fig. 3). Therefore, when the plunger of one of the auxiliary switches C is in normal' position, the plunger 1s m electrical connection with the bolt ci, but insulated from the I main section of the shaft 43.

The master switch H is substantially the 'same as the master switch E, withthe eX- ception that it has no plunger shaft to control, as does the plunger shaft 43 of the master switch E. This master switch H is purely a circuit-controlling device.

The first and second selectors O and'P (Fig. 7 are a modified form of lthe selec-tor disclosed in United States Patent No. 815,321, granted March 13, 1906, to Keith, Erickson & Erickson; while the connector switch R (Fig. 8) isof the type described in said connector Patent No. 815,176.

In Fig. 1G the trunking switches S and N1 are the same those in Fig. 6; and the master switch E1 is the same as the master 'switch E-of Fig. 6, with the'exception that one row of bank contacts has been removed and given to the control of the master switch .-G, which master switch Gr is given control,

position, having been driven romthe first position by the seizureof the first trunk,l

line by the individual switch J. It will be seen that the wiper of the master switch H is likewise shown resting'on the second-con? tact. The wipers of these two switches E and H, however, operately absolutely independent of each other,`there beingr no relation between the twoas far as their 'position relative to their bank contacts are concerned. It will be assumed that the subscriber 4at substation L (Fig. 6) calls the subscriberI M (#2220), Fig.. 8. l"The calling subscriber removes -hisreceiver from the switch-hook, thus unlocking the dial, inserts his finger in the finger-hole .marked'2, corresponding to the first digit to be called, turns down the dial and then releases it. Upon drawing the dial down the rotary impulse tooth 31 presses the rotaryimpulse spring. 27 onto the ground post 33, and thereby causes a momentary impulse circuit to. be established through the trip magnet 44 of the line switch J, including the central station battery B. The

impulse circuit through said trip magnet 44'- eil-tends from ground G2 throughthe ground springs 12 and 11 to the rotary impulse spring 27, rotary line conductor 17, conductor97 (Fig. 4),*bridge-cut-otl' relay springs 65 and 66, trip magnet 44 to the battery lead 98, and through battery B to ground G.

The trip magnet 44, upon energizing, at-

vplunger 42 enters the terminal q, the springs 55l and 58 are4 pressed into contact, as well .as the 'springs 59 and 62, the springs 5.6

lal'ldf'?, and the springs 60 and 61. Furthermore, ytheprojection 99 on the plunger arm '4 7, upon rising, closes the springs 100 and 101 into contact.

The closure of contact i betweenthe springs' 100 and 101closes'an .4L may vbe called',.in order to prevent any subseriberfrom 'calling-in upon this call-K ing line'li after a cali has been started. Thev l energizing circuit throughy the'l cut-oit relay 63 from ground Gd through the springs 101 and 100, through the cut'fotf 'relay 63 to the battery lead 98, and through battery B to ground G- The said springs 100 and 101 are susceptible 4of adjustment and,l if desired, may-be. 'so adjusted thatthe relay 63 may become energized,beforel the plunger 42 Acloses the bank springs, already7 men- -tioned, into contact. As soon as the cut-ofi' relay 63 .energizes, its armature separates the springs 64, 65 y and 6,6, thereby removing the short-c ircuit bridged across the line conductorsl and 17, and at the same time" disconnecting the trip'magnet 44 from the lines.

in order -to prevent further .energization of theA ,said trip" magnet. The. closure of contact between the springs 100vand 101,'furthermore, sets up a guarding potential over theI so-called vprivate normal conductor 102 that leads to the private bank 'contacts ofA all connectors through which the substation closure of contact, between the 'springs 59 and gllextends thev subscribers Yertgtcalj line' conductor 16 to the vertical trunk conductor 103. The closure of contact between the 'springs 60 and 6l extends the subsciibers rotary conductor 17 to the rotary trunk conductorl04. When the. springs 55 and 58 close into contact a circuit is established ythrough the trip magnet 95 of the auxiliary line switchN, over the following circuit, for tripping .said switch: from ground G* throughthe springs 55 and 58, through the cut-oi` relay springs 106 and 107 (the relay 92 being denergized), conductor 108, contact point 82 of the master switch bank K, master switch wiper 70, common segment w',

' conductor 109, master switch wiper 110, contact pointlll of the master switch bank T, conductor 112, plunger 94, socket 113, con ductor114, trip magnet 95 to the battery lead 98, and through battery. B to ground v G. At the instant that this circuit is closed, it will be understood that the master switch wipers and 110 are in engagement with the lirst contacts of their respectivebanks K 'and T. Also, the closure of contact bei l tween the springs 56 and 57 sets up a nongrounded guarding potential at the master switch .bank contact 83,through the release magnet 45 of the line switchJ, as follows:

from the contact point 83 to the conductor 105, bank springs 57 and 56 to the release `magnet 45, thence through said magnet to the battery lead 98 and to battery B. This guarding potential drives the master switch E frornthe seized trunk line, the conductors 103- and 104 of which have been indicated, and ,also preventsthe master switch from subsequently selecting this. .trunk line before it becomes idle.l The operation by which th'e master switch E is driven from the.

seized trunk line is asfollows: As soon as the springs '56 and 57 establish the guarding potential at the master switch bank contact 83 a .flow of current is set up through the motor magnet relay 68 of the master switch E from ground G5 through thewinding 86 of the relay 68 to lthe conductor 123 to the common segment y, thence tothe wiper section a and to the contact 83, thence through the springs 57 and 56 and through the re lease .magnet 45 to thebatter .through battery B to groun lead 98,- and G. The re lay 68, upon energizing, causes the springs 88 and 89 to comeinto contact, thereby closing'the energizing circuit for the motor magnet 67, which magnet thereupon attracts its armature and rotates thev ratchet wheel 69 one step, thereb causing'the master switch wipers a an b to advance to the second position, as indicated in Figs. 4 and 5. Of course, the energizing circuit through` the auxiliary relay68 issbroken at the instantA that the wiper a leaves the 'contact 83,

but it will be evident that if the next trunk line happens -to be busy "the next bank contact, 1,24 will also have a guardingvpotential iet iiio

' 139. releasemagnet 96, springs 132 and 131 and the circuit will not be broken until the motor magnet 67 has caused the wiper to advance another step, or a series of steps, Auntil an idle position is found. The advance of the master switch, however, does not take place before the trip magnet 95 of the auxillary line switch N has time to operatively energize. As soon as the trip magnet 95 encrgizes, the plunger 94 is released and the bank springs 115, and 116 are brought into contact and also the bank springs 117 and 118, springs 119 and 120, and springs 121 and 122. The closure of contact between the springsll and 116, it will be seen, extends the connection from the trunk conductor 103 to the trunk conductor 125; the" closure of contact between the for the cut-off relay 92 from ground G6' springs 117 and 118 extends the connection from the trunk conductor 104 to the trunk conductor 126; and the closure of connection between the springs 119 and 120 extends the connection from the trunk-release conductor 127 to the trunk-release conductor 128. Also, the closure of connection between the springs 121 and 122 sets up an energizing circuit through the springs 121 and 122, conductor 129, cut-oil' relay 92 tothe battery lead 98, and through battery B' to ground Grv The relay 92,v u-pon energizing, separates the springs 106 and 107 in order to break the round connection between ground'Gat the in eswitch J andthe bank contact 82 of the master'switch bank K of the master switch E. lThe reason for breaking this ground r"connection will be explained. The projection 130 on the rear end of the plunger shaft gize'. The energizing circuit for said relay" 133 extends from ground GrT at the master switch H' through the winding 134 of the i relay 133,cond`uctor 1 35, to the common segment .1 36 of vthe master switch bank T, through the tip section 137 'of themaster switch `wiper to the contact 138. conductor tothe .battery lead 98, and through battery -B to-ground G', The relay 133, upon attracting its armature, closes the springs 140 and 141 in Contact, thereby closing the energizing circuit for the motor magnet 142 from ground, G5 through the springs141 "and V140, through the `interrupter springs 143 and 144 to'the motor magnet 142, thence to vbattery lead 98., and through battery B to Such 'normal conductors are,

ground G. The motor magnet then 4attracts its armature, and in the same manner described in connection with the master switch E the wiper 110 is advanced onto the 4nextset of contacts, breaking the energizing circuit for the relay 133 as soon as'the wiper terminal 137 leaves the contact point 138, thereby bringing the master switch to a'- standstill` It will beevident that when the master switch E operates. as previously described, all idle switches B (Fig. 1) are advanced to a position opposite the next trunk line leading to the auxiliary switches C. It will also be evident that all idle auxiliary switches C will be advanced by the same master switch E to a position opposite the same trunk' line.A It will also be apparent thatwhen the master switch H stops, the

'wiper110 thereby selects another auxiliary switch, which will be operated or tripped by the next line switch B that makes a. call.V The relay 92 is made to break the ground connection between the ground G* and the master switch contact 82 for this'reason: The wiper 110 of the master switch H being in engagement with the second bank contact 145, there is a trip magnet 95 of some other auxiliary line switch, similar to the switch N, connected with the common member w of the master switch K. Then.if for any reason-the master switch E acts in advance of the inaster switch H, so that the wiper returns to the contact point 82, while the master switch H remains withthe Wiper 110 in engagement with the contact point 145, this second auxiliary switch would be tripped by the closure. of the circuit between the contact point 82 and the common mem-` ber m', and the springs 106 and 107 separated by the relay 92, even though the master switch E could not remain on -the4 said contact 82.A The passing contact would be sufficient to cauti a vtripping of the line switch, and it is for this reason that thisA arrangement is provided. After the subscribervs line is extended to the trunk 'confluctors 125 and 126, and, therefore, to the, irst-seleetor the said selector switch O is operated inthe usual manner by the vertcal impulses corresponding to the first digit 2 of the number 2220. which impulses are transmitted as the dial returns. This selector O, it will be understood, differs from the selector of the patent aforesaid in that the so-called normal conductors are omitted from across the conductors 125 and 126. however, shown at 146, 147 and 102 (Fig-6), and are known as the Vertical, rotary and private normals. Another difference is that the line, relays 149 and 150 are connected directly to the battery instead of through the contacts controlled by a s oscallcd b'ridee-cut-ol relay. This selector O is, of course, in addi# tion to the line relays 149 and 150, provided with the vertical, rotary, private and'release magnets 151, 152, 153 and 154, and also with the back-release relay 155. It will be seenthat another diffcrence'in the selector O is that the release magnet has one terminal connected with the battery lead 98, and the other terminal connected to the so-called trunk-release spring 156 instead' of the private magnet spring. When both the 'line relays 149 and 150 are energized simultaneously the trunk-release spring 156 is adapted to engagel the spring 157, for the purpose of energizing thev release magnet 154 before the side switch passes to second position. The side switch, of course, comprises the side switch wipers 158, 159, 160 and 161|. These wipers are all rigidly connected and are controlled by the private magnet 153.A

The'side switch is adapted to assume any one of three positions known as the first position, indicated by the dotted line, the second position and the third position, indicated by the full lines. that the back-release relay 155 is adapted to energize the release magnet 154 by pressing the spring 162 onto the grounded spring 163. The second-selector P is exactly the same as the selector O, with the-exception that the trunk-release spring 164 and the back-release relay spring 165 are connected to the trunk-release conductor 166 instead of to ground. Since two vertical impulses are delivered to the vertical line conductor 16 when i thevertical line relay 149 of the selector O' the vertical impulse teeth press the vertical impulse spring 26 onto the ground post 33 twice, upon the return motion of th'e'dial,

ground spring'168, thereby energizing thel verticalmagnet '151 by a flow of current from ground G through thel springs 168 and 167, through the private magnet springs 169 and 170 vto the vertical magnet 151, and thence` through said` magnet to the battery lead 98, and through battery B to ground G. The vertical magnet 151` upon attracting its armature, raises the switch shaft (not shown) twosteps, and. of course, the shaft wipers 171,172 and 173 to the second level of the switch banks and opposite the .first contact of said second level. After the vertical impulses, have thus been transmitted, the 'rotary impulse tooth v31 then presses the It will be seen ywill not operatively energize. y magnet 153, upon energizing, relie'ves'the.I

rotary impulse spring 27 .onto-the ground1v post 33, thereby delivering one impulse to the rotary line 'conductor 17, whereby the rotary line relay 150 of the selector 0 is energized once. The circuit of thisimpulse extends from. ground Gr2 at the substation to the ground post 33, thence to the rotary impulse spring 27rotary line conductor 17,

to ground G.

through` the private magnet 153 from ground 'i G through the springs 168 'and'174 to' said private magnet, and thence to thefbattery lead 98, and through `battery B to ground G. The private magnet, upon energizing, causes the side switch to trip to second tion, by which operation an energizing circuit is established for the rotary magnet 152 when the side switch wiper 160 engages posithe contact point 175. This energizing circuit for the magnet extends from ground i 10 to the contact point 175, side switch wiper 160, interrupter springs 176, rotary' magnet 152 to the battery lead 98", "and through battery B' t0 ground G. .Tt may be stated at this juncture that anyofrtheinterrupters used in this system may bfof the type shown. As soon as the rotary magnet 152 attracts its armature thelshaft wipers 171, 172 and 178 are rotateduinto "en gagement with the first set of contacts of. the

second bank level.k 'If the trunk line terminating in this set of contacts-is idle the rotary armature, bydepressing and?. releasing the armature of the privatemagn'et 153, 4 causes the side switch to tripv from second to third. position, thereby destroying the energizing circuit for the 'rotarymagnet 152. But if the `first trunk line is busy the bank contact engaged by the private: wiper 173 will be grounded, for reasons tob`e vein,

plained, and asa result an energizing circuit is closed through the private magiie 153, said circuit extending from the saxldl contact to the private wiper 173, throng the back-release relay 15,5 totheside switch wiper 161, thence throught'he'private niagnet 153 and to the. battery lead' 9B. thence through battery B to ground G. The private magnet 153 is of such high resistance compared with that of the back-releasevv relay 155 in this circuit that the latter '(155) The private rotary magnet of 'its control overthe prit vate magnet arma-ture befpre the `vrotary magnet denergizes, A s a'iresult the Iside" switch is retained in second position, even after the rotary arm falls back, with the result that the rotary magnet is again ener* gizedand the shaft Wipers advance another step. This operation continues, of course, as long as the private wiper 173 continues to lind busy contacts. But at the instant that an idle Contact is found the trip magnet circuit is broken and the private magnet armaf ture is brought under the control of the switch 'Pi :'It the same time, the rotary trunk conductor 126 is placed in connection With the Wiper 172, by the conductor 179, and through'rsaid Wiper 172 with the trunk conductor 180 'also reaching to the switchI P. Furthermore, when the. side switch Wiper 161 passes intov engagement with the contact point`181, which is grounded, a guard- `ing potential is established at the private wiper 173 from ground G11 through the back-release relay 155, which is of low rei sistance, to the private Wiper'173. 29

Asv a result'lthe engaged bank contact is also `.grounded, and, therefore, all other contacts fait' ,connected in multiple therewith, for the 'purpose of preyenting the switchV P from being-seized by some other switch. The subscriber having advanced. the call thus --r"far, again rotates the dial for the digit 2,

.sending apreliminary impulse to the rotary .line conductor 17 and two impulses to. the vertical line conductor 16, and again another impulse to the rotary line conductor V17." At this stage ofthe operation it should be explained that the first impulse to the Vrotary line conductor 17 for the secondl Adigit is1of no consequence.

impulses to the vertical line conductor 16 However, the

pass through the bank springs 59 and ,62, vertical tru'nk conductorl 103, bank springs .,115 and 116, vertical trunkv conductor 125,

sideswitch Wiper 158 (Fig..7), conductor 177, shaft Wiper'171, trunk conductor 178 `tothe side switch Wiper 183, thence to the vertical line relay 182 and to the battery.

` lead 98, thence through battery B to ground G. ".Ihe vertical line relay 182 operates to energize the `vertical magnet 184 in the 1nann er al eady described in connection'with the switch O, and as a result the shaft Wipers 185, 186 and 187 are raised to a position opposite the first contact of the second bank level.v "After this has been done thelast impulse to the rotary line 17 energizes the rotary.l line relay 188 over the tollowng circuit: from ground G2 to the roy tary line conductor 17, thence through the .springs 61, rotary trunk conduct-or 101, bank springs 117 and' 118, rotary trunk conductor 126, side switch wiper'159I (Fig. 7), conductor 179, 'Wiper 172, trunk conductor 180 tothe rotary line relay 188, thence to battery lead 98, and' through battery B 4to ground G. The rotary line relay 188, upon energizing, in turnenergizes the private magnet 189, by Awhich operation the. side switch is tripped to second po sition, whereby the side switch wiper 190 is put in engagement with the grounded contact point 191, and the energizing circuit for the rotary magnet 192 thereby closed. The rotary magnet then operates, in the manner explained in connection with the selector O, to rotate the shaft Wipers 185,

186 and 187 into engagement with some idle trunk line the conductors 193, 194 and 195 of which are shown terminating in-the connector switch R. Having thus extended the line to the connector R the subscriber again operates his dial for the third digit 2, grounding the line conductors 16 and 17 as before. The first impulse to the conductor l7,.ot course, is of no consequence; but the two impulses that are given to the vertical line conductor` 16 energize the vertical line relay 196 of the connector R. The energizing circuit, it will be see-n, ex-

tends from the substation ground G2 over the.

conductors 16, 125, 178 and 193 (Figs. 6,

l7 and 8) on the vertical side of the main line to the vertical line relay 196, and thence through battery B .to ground G. This relay .196, upon energizing, forces the 'spring 197 onto the ground spring 198, thereby` energizing' the vertical-magnet 199 by a.

How of current from ground G12 tlirou'ghl the springs 198 and 197, and through the prIvate magnet springs200 and 201 to the side switch wiper 202, vertical magnet 199 to the batteryY lead 9.8, thence through .bat-z tery B to ground G. The vertical magnet.

operates to raise the shaft Wipers 203, 204 and 205 to a position opposite the first` contact ofthe second level nf the connector banks The rotary impulse to the' line conductor '17,-afte'r this has been done, energizes the rotary line relay 206 by a flow of current fromv ground .GF over the rotary conductors v17,104, `126, 180 and 194 to the said relay 206, thence through battery B to ground; G. `The said relay `206 then presses the spring 207 ontoV the ground I spring 198, thereby energizing the privat-c.. rrent from'ground magnet 208 by a How ofcl G12 through said magnet 208 to battery B'. t

As a result the side.V switch is tripped "to second position, when the magnet 208 energizes and de energizes.` -By this operation the side switchvviper 2021 is shifted from the contact point 209 of.therst` position' v. to the contact 'point 210 of the second position, thereby substituting the .rotary magnet 211 for the vertical magnet. 199, bringing" the former under the control of the verticalV again energizes the rotary line relay 206.

at the connector R by a flow of current over the4 circuit reviousl'y described. The rotary line re ay 206 in turn operates, again ener 'zin the private magnet 208, whereby'ft e si e switch is tripped from second to third position, with the result that the trunk conductors 193 and 194 are extended into connection with the shaft wipers 203 and '204, res eotively, whereby the calling s'ubscribers ine is thus placed in connectionwith the called subscribers line. It will be seen that by this operation the vertical line conductor 16 of, the calling line is placed in connection with the' vertical line :conductor 212 of the called line, and that therotary line conductor 17 of the calling line is placed in connection with the rotary line conductor 213 of the called line. The ircuits connecting the 'conductors 16 and 7 and. the. conductors 212 and 213 are indicatedibythe heavy conductors in Figs. 6,

` 7 and 8 and, as shown, include the condenser 214 on'fhone side, and the condenser 215 on the other side. When the side switch passes to' third positiomthen not only is the callin line extended into connection with theca led line, but a guarding potential is also established at the private wiper 205 from groundG", whereby allprivate bank contacts Aallotted to the called line are provided'withniea-ns for preventing any other subscriber from-calling `the line #2220 while itis busy. Also, .when the side switch Wiper 227 passes to third,position,*while the private iviperf205-engages the private contact .of the called. line, an energi'zin established.' thi-foul h the cut-o vrelay 22!l` of the line switch 'of the called line', wherecircuit is by. the.- short-'circuit that normall exists across thev line is-cpened, andl att e 'same time the trip magnet is disconnected from theline. tablished the calling subscriber may signal the called subscriberby pressing the button .38 and thus grounding the vertical line conductor 16. As a result the. vertical line relay 196 of the connector R is energized,

. which in turn causes-the energizing of the ringer relay 216 by ailow of Acurrent from lupon energizing,

The vertical.

'station #2220 is rung.

` and among other After this circuitv has been. es'- lease conductor ground Gr"x to the side switch wi thencg through the ringer rela 21 tery and to ground G. e rela 216,

it will beseen, isconnects the calling line from the called line and bridges the ringer generator U across the latter, whereby the bell 217 of the sub When the called subscriberanswers it,will -be seen that the ringer 217 is disconnected from across the line, and that the circuit including the receiver 218 is bridged`instead, whereby the called and calling subscribers may conversel over the heavily marked circuit indicatedv in Figs. 6, 7 and 8. AAfterthe subscribers are through talking, called subscriber may release the connection. If the| calling subscribers hangsul'' his re-v ceiver irst, lhe will releaset e conn the line conductors 1B and 17 simultaneous y when the release s rings 18 19 and 20 come into contact. rounding'.` these conductors simultaneously energizes' the line relays 206 and 196 of the connector R simultaneousl whereby the trunk-release springs 219 an 220 are ressed into 'contact. As a result the re ease magnet 221 of the connectorR'and the back-release relay 222 of the second-selector P (Fig. 7) are energized in series by a low of current fromground Gru at the selector P through the side switch wiper 223 to the back-release relay 222, thence over the conductor 2 24 to the private wiper 187, trunk-release springs 219 and 220 -of the connector R, thence through the batteryl lead 98, and through battery B to ground G- The'release magnet 221,

upon energizing, attracts its armature and thereby restores. the connector side switch and switchshaft, as is well known. Upon the restoration of theshaftthe wipers there of are disengaged from the bank contacts,

Y results the circuit through the lbridge-cut-oi relay 225 is broken,

.whereby the said relay 225 is restored. At

the Sametime that the releasemagnet 221 energizes, the back-release relay 222 of the second-selector lay 222 then drives `inta contact. lished', including inseries the release mag' net 227 of lthe selector P and. the' bac b groundin thesprings 226 and 165' -`release relay 155 of the selector O. circuit extends from ground G11 at theselector O tothe side switchvwip'erl161, then through the backqelease relay 155- to the 'conductor 228,' private wiper 17 El, trunk-re- 166, back-release relay springs 165 and 226 to the-release magnet 227, thence to the battery -1ead598, and through battery B to ground G. The re-l lease magnet 227 of the selector P then attracts its armature and remains' in readiness to release the` switch P as soon as the either the calling or ection loo i the release magnet 221.` to i also energizes ,which re- Acircuit is thereby estab-4 the switches N andv J (Fig. 6). The release magnet 154 of the selector G being energized attracts its armature and remains in readiness to release the switch O as soon as the energizing circuit is broken, and the same is true with regard to the release magnets 96 and 45 of the switches N and J. The energizin circuit for the release magnet 154 extends rom ground G through the sprin 163 and 162 to the release magnet 154, t ence through said magnet tothe battery lead 98` and through battery B to ground G. The energizing circuit for the release magnet 96 of the switchN also extends from ground G through the springs 163 and 162 to the trunk-release conductor 128, and thence through the release magnet 96 andthe springs 132 and 131 tothe battery lead 98. and through battery B to ground G. The vertical magnet' 45 of the switch J is in multiple with thc magnet 96 and its energizing circuit extends from 'the trunkrelease conductor 128 through the bank springs 120 and 11i) to the trunk-release conductor 127, thence through the bank springs 57 and 56 to the release magnet 45 to the .battery lead 98, thence through battery B to ground G. The cnergization'of a'll of these :release magnets, of course, isI practically instantaneous, and occurs at the time that the stvitclrhook.` on descending, retains "the release springs 18, 1f) and Q0 in contact.

As the sujitchhook 3 descends the said release springs 18. 19 and 2O disengage and the line relays 191i and Q06 tthe connector R deenergixc` cmrplctely restoring the said connector. As soon 4as the trunk-release springs 219 and 220 separate. the energizing circuit for thv l'mck-release relay Q22 of the selector P is broken. which in turn, upon dciinergizing, breaks the energizing-circuit 'of therelease magnet. '227, and of the backrelease relay 1550i? the self-dort). This relay 155 in'tuin, upon detinei'gizing.' destroys the energizing..circiiits for the release mag- 'net 154,401: theselector t), the release magnet 96 idf tle switch N, 'and' the release mag` net 4:31 ot the switch J. By this operation .theswitches'P'and O are completely released andrcstoedfto normal'e'ondition, and also theswtches N and J: By `referring to. Fig. 4 itwill he seen that when the release magnet '15 energizes. the portion 51 of the trip magnet arrnature` rises andv 'latches the near'portion 526i the plunger arm 47. Then vwhen the release :magnet45 'denergzes the plunger amn47 is,"of coursefufrawn down so that the plunger 42 iswithdrawn from the bank Q,r and restored to engagement with the plunger shaft. The releasing operation of the switches J und N (Fig. 6) being thesame, it will be clear how the switches are restored by their respective release magnets upon denergization of the same. If the called subscriber had rest-cred his receiver 218 before the calling subscriber, nothing would have occurred unless he had previ ously operated his dial so as to bring the ground springs 229 and 230 into contact. In this event the back-bridge relays c31 and 232 would have energized simultaneously, so that the baclcbridge relay springs 233 and 234 would have been brought into contact, with the result that the release magnet 221 of the connector would have been energized, and the connector 'switch restored, thereby breaking the. energizing circuit of the bridgecut-off relay 225'of the line switch S ot the. called line. The energizing circuit for 'said release magnet, in that rase, would extend from ground (im through the springs 233 and 234 to the release, magnet. 221. thence through battery B to ground G. Of course, the callingr subscriber. upon hanging up his receiver subsequently, would energize the line relays 196 and 206 of the connector R, causing the release of the ren'laining switches, as previously explained.

It will be evident' that if the called sub# scribers line is busy the'eonnector switch. R will be released at the. instant that thailast rotary impulse is sent in. As previously dc scribed, this rotary impulse4 energizes the private magnet 208, and as u result the private ma ffnet s urines Q35 and 236 are brought 199, which inturn causes the switchshaft to 'be raised, thereby closing into contact the switch Vshaft springs Q39 and 240 at the connector R, and establishing a busy-signalling circuit from the busy machine V through the calling substation to notify the calling subscriber that the line is busy. Upon hanging up his receiver, of course, the calling subscriber will; initiate the release already described.

The forel `Jing, therefore, describes how the'subscriber L, Whose line terminates Iin the Vmam exchange, may call the subscriber M, whose llne terminates 1n a distr1ct or auxiliary exchange. Now it remains to explain how thesubscriber M of the district exchange may call any other subscriber. As far as the subscriber M is concerned the. mode of operation is the same as that described in connection with the subscriber L, but the arrangement of the apparatus by means of which the subscriber M obtains connection with a first-selector is slightly different from that illustrated in Fig. 6. This arrangement is clearly shown vin Fig. 16. There is substantially no difference in the circuits, the difference being in the me chanical arrangement. In Fig. 16, of course, the 'line switch S is=the line switch of the subscriber M, which is also shown in Fig. 8. Theauxiliary switch N" is exactly the same as the'auxiliary switch N (Fig, 6). Also, the master switch H (Fig. 16) is exactly the same as the master switch H (Fig. 6), while the master switches E and Gr take the place of the master switch E (Fig. 6). The only dilference between. the master switch E' and the master switch E is that the upper half of the bank K, comprising the contacts a: and the common segment w', has been removed 'and given to the master switch G. This master switch Gr is located at the main exchange and has a wiper, similar to the wiper of the master switch E, which travels over lthe vbank contacts. Furthermore, this master switch G 4controls the plunger shaft F that controls the plungers of the auxiliary switches of the group of which the auxiliary switch N is a member.' One difference inthe electrical cireuits,'to which reference has been made, is thatthe motor magnet 241 for operating the master switch G (Fig. 16) has no interrupter of its own, but 1s connected in series with the motormagnet 67. of the master` switch E, for the purpose of always main-- taining the wipers of these two 'master switches in synchronism, so as to4 insure the idle switches of the group C being always opposite the same trunk line.v

From the foregoingit will-be seen that I 'provide primary and secondary non-numerical automatic trunking switches, with trunks between them, whereby any calling sub-" scriber must extend a connection through two, non-numerical trunking-switches before obtaining connection with an idle first-select`or. The primary vnon-.i'iuxun'erical trunking switchesJ'are the same in" number as the subscribers telephone lines, and the secondary noli-numericaltrunkin-g switches N are the same in number Aas the first-selectors. The intermediate trunk lines, such as( the trunk'line comprising the conductors 103 and 104, .canl be arranged on a' 'percentage basis, relative to the number of telephone lines. and can beeither moreor less in 'number than the 'secondary non-'numericalt'runking switches N, according to .requirem nts. Furthermore, I find that with this arrav gement the work is more evenly distributed between the different trunk llnes andthe first-selectors, so that the subscribers in the group are not liable to use one trunk and one first-selector more than the others, as the calls are more evenly distributed between the different trunks and switches. It will be seen that the said intermediate trunks are each provided with a set of multiple bank terminals at each end thereof, and that there are noautomaticl switches each of which is individual to one of said intermediate trunks. These intermediate trunks are one-way in character, being adapted for calling onl in one direction, and do not terminate 1n switches for selectin other lines or trunks. In this way the only matic switches associated with these intermediate trunks are the switches that are employed 4for selecting said trunks, and there are no selectors or trunking switches in which these intermediate trunks terminate for selectin other trunks. A calling subscriber, there ore, causes his individual switch to automatically select an idle trunk, and at the same time causes another automatic switch to select the same trunk, preferably art the other end thereof.

` In this system it will be obvious that the resistances o f the magnets may be varied to any-extent consistent with` the successful operationof the same. I Not only may the re'- slstances o f`4 the line relays or example,

.relays 196l and 20.6) of the connector'be varied, but the resistances of; the operating magnets (for example, the release magnets auto- 221, 227, 154, 96 and'45) may likewise be varied. It is also obvious that the springs used as contacts may be adjusted in any; de-

sired manner, and theirtensions varied to any extent in order to control the speed and operation of the armature associated with them. For example, the springs of ,the motor relays` B8 and 133 may be stiened or weakened asmayfbe Afound convenient or desirable.

What I claim as my invention is 1.v In atelephone automatic trunking sys-v tern, a calling telephoneline, a plurality o'f trunk lines, a vplurality of progressively movable automatic switches associated with said trunk. lines for calling purposes, and means for selectingl an idle trunk line ahead of the call, any one of said automatic.

switches being responsive to en impulse vfrom the calling subscriber for seizing` the said preselected trunk line.

2.' Ina telephone automatic trnki tem, a calling telephone line, a plural ty of trunk lines, a pluralityr of. progressive]K movable automatic switches associated wit said trunk lines for calling pur .oses, and means for selecting an idle trunk ine ahead of the call, said automatic switches being responsiveto an impulse from the calling subayescriber' for seizing opposite ends of the pre selected trunk line.

3. In an automatic trunkin system, a calling line, a trunk, a set of mu ti. le terminals -for each end of said trunk or use in seizing the sume, a separate non-nuinerical automatic switch for each terminal, a progressively movable switch, said non-numerical switches responsive toV the calling line for extending connection from said line to the trunkaiid to said progressively movable switch, said, last mentioned switch controlled from the line for cxtendiiig a conuection beyond the trunk.

4. In a telephone automatic trunking system, a plurality 'of trunk lines, subscribers individual non-numerical trunking switches for seizing'irlle trunk lines, a progressively movable 'automatic switch, and other automat-ic switches for selecting and seizing the seine trunk lines, ,whereby each trunk line when brought into use by a -calling subscriber is'always seized by the sutscribers individual switch and one ofr said other automatic switches, for extending connection from a line to the trunk/audio said progressively movable switch, said last mentioned switch controlled from the line for extending a connection beyond the trunk.

5. In a telephone automatic trunking system, a plurality of trunk lines, subscribers= individual noir-numerical trunking switches for seizing idle trunk; lines, a progressively movable automatic switch, and other autoinatic..switchcs l'orsclecting and seizing the sanietrunl lines, whereby each .trunk line when brought into use by a calling subscriber is always seized at oneend by 'the subscribers V.individual switch and at thel other end by one of said automatic switches, for extending connection from a line to the trunk and to said progressively 'movable switch, said last mentioned switch controlled from theline for extending connection bevyond the trunk.

6. AIn a telephone system, plurality of subscribers individual vtriinking switches, a plurality of. first-selectors less in number than the subscribers individual switches,

trunkjlines leading to the first-selectors,. i trunking switches at the otherendof 'saidV trunk lines,` and trunks leading' from the ini `dividual switches Ato saidV last-mentioned .,switches, eaclrtrunk provided with a set of .5,5-

multiple terminals ateachiend thereof, each 4-terniinal located. Vina diferent "switch, and .V each. trunk adapted. for one-way'. trunking only. i i

7. In an automatic telephone system, a plurality of firstfselectors, trunk lines leading to said!` irstfselectors, an automatic trunking switch at the other end of each trunk'line, allotted thereto, and"suitab le instrumentalitiesffor automatically selecting Lacasse adapted for one-way t and trunking al calling subscriber to anidle one of said automatic trunking switches, said switches responsive to im ulses from the calling subscriber to exten a connection to a called subscriber.

8. In a telephone automatic trunkingsystem, a plurality of trunk lines, a plurality of automatic switches, a calling telephone line, means for causing said switches to select an idle trunk line'ahead of the call, said automatic switches bein responsive to the calling subscriber for seizin the said preselected trunk line, each tru line comprising a third conductor, and trunk-release circuits includingsaid third conductors.

9. In a telephone automatic trunking system, a plurality of trunk lines, a plurality of automatic switches, a calling telephone line, means for causing said switches to seof the preselected trunk line, each trunk line comprisin a third conductor, and

trunlcrelease circuits including said third conductors.

l0. In. a telephone system, a trunk line, means for selecting opposite ends of said trunk line, non-numerical automatic switches lresponsive to a calling subscriber forseizing opposite ends of said trunk line in making a call, each trunk line comprising a third conductor, and trunk-relea5e circuits includingsaid third conductors.

1l. In an automatic trunkin System, a one-way trunk, a Set Yof multip e terminals for eacliend of said trunk,a separate noniiumcric'al automatic switch for each terminal, each4 trunk comprising a third conductor, and trunk-release circuits including lsaid third conductors. V

l2. In a. telephone system, a trunk line, a set of multiple terminals for each end of said trunk line, each terminal located in a dill'ereiit bank, suitable non numerical sii-'itching instrumentalities for. connectin with a terminal at each end of said trun line whenever the latter is to be employed for extending connectionv from a calling to a called subscriber, :each trunklinecornp'rising a third conductor, and Vtrunk-release circuits includin'gsaid third conductors.

i3. In a tele hone system, a' plurality of subscribersin ividual trunking switches, a

than the subscribers individual switches, trunk lines leading vto the first-selectors,

` trunking switches at the other end'of said terminals at each end thereof, each terminal locatedin adiil'erent switch 'and each trunk ing only, each plurality of lirst4sele'c'tors less in number 

